TBI vs LS replacement

[Kudzu]

I have a near mint 93 Suburban and it's time for a engine, I hear a rob knock on startup. My Suburban is a driver, I use it around town and we take it on road trips. Very seldom tow any more than a small trailer with a load of lumber or a lawnmower. When I get my wood boat I am restoring I will be towing it on short trips to the lake. looking at around 2,500 lbs boat and trailer

Looking at the costs I had decided on a replacement Vortec Crate motor running it with the TBI, short tube headers, better intake and MAYBE a cam swap? Looking for more low end to mid-range power.

I have been reading on LS swaps and have been seriously considering one. I understand the extra work that installing an LS would take, the extra work is not lost on me. I know an LS is a 'better' more advanced engine. But when it comes down to the practical, drivablity of a 300-325 hp engine am I really gaining enough to make it worth the extra work and expense? I had pretty much decided to go that way but having serious second thoughts. Just looking for some input.

[Fast355]

If you do a LS swap get a 6.0 or 6.2. The 4.8s and 5.3s are gutless unless you really spin them high. Even then a small cammed LQ9 6.0L with bolt-ons did not even make the same torque my mildly cammed 350 Vortec did at 3,400 rpm until 4,500 rpm. Same dyno, same day and the 6.0L truck had a 4L65E and 8.6 rear end vs my 4L85E and 9.5". The 6.0L also had electric fans where my 5.7 has a massive power sucking duramax clutch fan and HD fan clutch. 6.0L peaked at about 5,400 rpm in HP where my 5.7 peaked at 4,700. 272 rwhp @ 4,700 and 330 rwtq @ 3,200 from my 350 with the tiny 395' marine cam aka Ramjet/HT383 cam. I put the GM 357 HP 350 HO crate engine cam in it and bumped the power to 285 rwhp @ 5,500 /340 rwtq @ 3,800. Compared to the 395' cam power was better everywhere from 2,500+ My 5.7 has slightly worked heads with 2.02/1.60 valves, slightly higher compression from milled heads and a .016" thick shim head gasket, 1.7 rockers, tri-y headers, ported marine intake, and a decent exhaust. I recently dyno'd 12 rwhp and 3 rwtq more with open 2.5" cutouts between the cats and muffler for a total of 297 rwhp and 343 rwtq. That was also on E85 with 34* total timing. Even with the 215/223 @ .050 cam and the 1.7 rockers giving a .537" lift in my 350 the 6.0L with a smaller 212/218 high lift cam could not match the 350s torque until 4,500 rpm. Because of the head and intake design it went on to make about 20 hp more but gave up over 40 ft/lbs down in the 2,500 rpm range. With his driveline my numbers themself would have been about 5% higher. I already have a 4-bolt main 6" rod 383 sitting on the stand with a 10.5:1 compression ratio and Edelbrock Etec 170 heads. Cam will be a 224/236 @ .050 roller cut on a 108* LSA with .554/.554 lift. I am dropping the 1.7s and going with 1.5s this time around.

[Kudzu]

Since it is a street car I am more interested in low end torque. I have to keep reminding myself of this because it is easy to get caught up in HP search. If I go with an LS I am going to have to buy a used engine along with the harness to stay in my budget. If I could find a low milage total I could part it out and make some of the money back but not sure I really want to get into that much work. I have enough projects as is.

I am still thinking on this but the more I look at it I am leaning toward just buying a replacement Vortec engine and putting the TBI back in.

[lionelhutz]

Overall, I'm not sure it's worth it for what you would gain. You'd like driving a 6.0L LS more but the gains just might not justify the extra work in your case. Here is some info to consider.

A 5.3 LS will pull harder than the stock TBI engine and it will use less gas. The 5.3 LS would not have as much low end torque as the Vortec engine though so overall you'd have to spin it at a little higher rpm to get the same power. But, they love the rpm and it's not a big deal. You would hardly know you are doing it. Still, I'd consider it to be about even on drivability compared to the Vortec so the extra work to swap one really wouldn't be worth it unless you could do it cheaper.

A 6.0L LS beats a stock Vortec torque curve pretty much everywhere. Still, it's fairly evenly matched up to the Vortec peak torque. Then, the 6.0L pulls even harder up to it's own peak torque. However, add in the fact that LS engines love to rev so it's easy to turn them a little higher and the 6.0L will easily out-run the Vortec during normal driving. Don't believe anything about a stock Vortec having way more low end torque compared to a stock 6.0L LS because it's not true. Here are some numbers.

Vortec:
255 hp (190 kW) @ 4600 RPM
330 lb·ft (450 N·m) @ 2800 RPM
about 300 lb-ft @ 1400 RPM

first gen 6.0L
300 hp (224 kW) @ 4400 RPM
360 lb·ft (488 N·m) @ 4000 RPM
about 340 lb-ft @ 2800 rpm
about 300 lb-ft @ 1400 rpm

As another consideration, an electronic transmission is really nice if you spend the time to tune it. Fine adjusting the shift points to match your driving expectations can make a big difference in how nice you find the vehicle drives. You can pretty much get it to be in the gear you want all the time. You could also get this with the TBI by using a PCM and newer transmission.

[Fast355]

Overall, I'm not sure it's worth it for what you would gain. You'd like driving a 6.0L LS more but the gains just might not justify the extra work in your case. Here is some info to consider.

A 5.3 LS will pull harder than the stock TBI engine and it will use less gas. The 5.3 LS would not have as much low end torque as the Vortec engine though so overall you'd have to spin it at a little higher rpm to get the same power. But, they love the rpm and it's not a big deal. You would hardly know you are doing it. Still, I'd consider it to be about even on drivability compared to the Vortec so the extra work to swap one really wouldn't be worth it unless you could do it cheaper.

A 6.0L LS beats a stock Vortec torque curve pretty much everywhere. Still, it's fairly evenly matched up to the Vortec peak torque. Then, the 6.0L pulls even harder up to it's own peak torque. However, add in the fact that LS engines love to rev so it's easy to turn them a little higher and the 6.0L will easily out-run the Vortec during normal driving. Don't believe anything about a stock Vortec having way more low end torque compared to a stock 6.0L LS because it's not true. Here are some numbers.

Vortec:
255 hp (190 kW) @ 4600 RPM
330 lb·ft (450 N·m) @ 2800 RPM
about 300 lb-ft @ 1400 RPM

first gen 6.0L
300 hp (224 kW) @ 4400 RPM
360 lb·ft (488 N·m) @ 4000 RPM
about 340 lb-ft @ 2800 rpm
about 300 lb-ft @ 1400 rpm

As another consideration, an electronic transmission is really nice if you spend the time to tune it. Fine adjusting the shift points to match your driving expectations can make a big difference in how nice you find the vehicle drives. You can pretty much get it to be in the gear you want all the time. You could also get this with the TBI by using a PCM and newer transmission.

Actually the Vortec 350 makes as much as 40 ft/lbs more than a 6.0 down in the 1,200-2,000 rpm range, stock for stock. In the 2,200-2,500 rpm range it will brake stall the same converter more than 200 rpm higher. The 350 in my Express in stock form was making close to 280 hp @ 4,500 and 380 tq at the flywheel at 3,000 rpm if you go off the 25% expected drivetrain loss of a 4L80E and 9.5" 14-bolt. Stock intake & exhaust manifolds, factory 3" piping to the cats, factory muffler, factory 2002 5.7 Express 0411 tune, descreened maf, K&N filter and tb lip removed, MFI spider cranked to 66 psi to match the OEM spider. Oh I forgot I also had the EGR disabled in the tune and blocked off at the valve with a plate between the intake and valve.

[ras"86]

Great information, my stock 94 350 is due to be replaced soon, possibly a 350 vortec will be an easy fix.

[Queencityspeed]

The LS swap would be a lot of work with little gains over a decent SBC. Wiring, Mounts, Exhaust & etc. Bolt in a decent small block, tune it and ride out. Just my opinion.

[lionelhutz]

Actually the Vortec 350 makes as much as 40 ft/lbs more than a 6.0 down in the 1,200-2,000 rpm range, stock for stock. In the 2,200-2,500 rpm range it will brake stall the same converter more than 200 rpm higher. The 350 in my Express in stock form was making close to 280 hp @ 4,500 and 380 tq at the flywheel at 3,000 rpm if you go off the 25% expected drivetrain loss of a 4L80E and 9.5" 14-bolt. Stock intake & exhaust manifolds, factory 3" piping to the cats, factory muffler, factory 2002 5.7 Express 0411 tune, descreened maf, K&N filter and tb lip removed, MFI spider cranked to 66 psi to match the OEM spider. Oh I forgot I also had the EGR disabled in the tune and blocked off at the valve with a plate between the intake and valve.

I don't care at all about your numbers. You have posted enough complete bullshit to show that none of them have any credibility. Previous crap like claiming numbers that the performance magazines with their typical over-inflated tests NEVER come close to matching with or that an engine with a cold-air intake and catback can put 50 ft-lbs more wheel torque down then it's factory rated flywheel torque. Add in the fact that you hate LS engines and you have no credibility. I liked the old small blocks and still have a few around, but have no trouble admitting that the LS engines can make more power.

You are completely full of shit about the L31 making up to 40 ft-lbs vs the 6.0L. Anyone who can use Google can look up this curve.



The LQ4 certainly DOES make hit 300 ft-lbs of torque in about the 1300-1400 rpm range. Add 40 ft-lbs and you're over the L31 peak rated torque.

Any claims about how a L31 does way more than rated after you do the simplest bolt-on mods is bullshit. Tons of people have proved that mods like MAF de-screening, TBI lip removal or catback exhausts pick up very minimal power.

Any claims about how a L31 picks up a bunch of power after more serious bolt-ons or a cam and tuning would also apply to a LQ4. It's not hard to find power in a LS engine with smart modifications and tuning.

[Fast355]

I don't care at all about your numbers. You have posted enough complete bullshit to show that none of them have any credibility. Previous crap like claiming numbers that the performance magazines with their typical over-inflated tests NEVER come close to matching with or that an engine with a cold-air intake and catback can put 50 ft-lbs more wheel torque down then it's factory rated flywheel torque. Add in the fact that you hate LS engines and you have no credibility. I liked the old small blocks and still have a few around, but have no trouble admitting that the LS engines can make more power.

You are completely full of shit about the L31 making up to 40 ft-lbs vs the 6.0L. Anyone who can use Google can look up this curve.



The LQ4 certainly DOES make hit 300 ft-lbs of torque in about the 1300-1400 rpm range. Add 40 ft-lbs and you're over the L31 peak rated torque.

Any claims about how a L31 does way more than rated after you do the simplest bolt-on mods is bullshit. Tons of people have proved that mods like MAF de-screening, TBI lip removal or catback exhausts pick up very minimal power.

Any claims about how a L31 picks up a bunch of power after more serious bolt-ons or a cam and tuning would also apply to a LQ4. It's not hard to find power in a LS engine with smart modifications and tuning.

I guess anyone can google this power chart too and realize what a L31 with a decent intake manifold will do. Remember he said nothing of using the stock Vortec truck intake manifold. The factory Marine cam is really no hotter than the truck cam. Marine L31 is 292 HP @ 4,800 and 370 TQ @ 3,200 with more than 350 ft/lbs @ 2,000 rpm. But what do I know. I have run a stock long block L31 in a TBI application with shorty headers and a 454 TBI unit on top of an edelbrock performer rpm intake manifold. It made over 300 HP at the crank and over 400 TQ at the crank. It did 260 RWHP/330 RWTQ through a 700r4 and 8.5 10-bolt with TBI.

http://www.gmpowertrain.com/2013_pdf...ine_010713.pdf

As for your factory rated power vs wheel power. My 2012 Titan put down 398 RWTQ on a stingy ass Mustang dyno and 296 RWHP after power correction. Real power was 6% higher than the correction in 45*F weather. The truck made over 300 RWHP and 400 RWTQ un-corrected. Same truck on a Dynojet made 330 RWHP. Factory rating was 317 HP and 385 TQ. Cold air intake, muffler swap, and a Hypertech programmer was all it had. On a 60*F sunny day on a decent track, it ran a 13.98 @ 98 on a 2.01s 60' with an open differential and well worn P275/60R20 Goodyears wrangler SRAs.

MAF descreen, TB lip removal, and K&N kept my MAP sensor from dropping above 3,500 rpm on the stock L31 setup. All stock it would pull down to about 90-92 KPA by 5,000 rpm on a 99-101 KPA baro. After the changes it would hold 96 KPA all the way to the 5,600 rpm fuel kill. The descreen also leaned the over-rich WOT air/fuel ratio down nearly a full point on stock tune. It was one of the first things I messed with and had a HUGE impact on how it ran.

[Fast355]

I have also seen numerous stock longblock, stock cam, stock intake manifold, stock head 350 vortecs put down more than 320 RWTQ once you open up the horrendous exhaust system they came with from the factory. The manifolds are not the worst part of MOST stock L31 engines. My Express van just happened to have a better factory exhaust system than any other factory LD L31 GM vehicle. Most of the trucks and SUVs used tiny 1 7/8" exhaust pipes between the manifolds and the mufflers with smaller cats. The Express van came out of the manifolds at about 2.5" and stepped up to 3" less than 6" off the manifolds and ran all the way to the muffler at dual 3". Makes a tremendous difference in power even with the stock manifolds.

[lionelhutz]

The numbers I posted are for the truck L31, not the marine engine. The marine cam had > 0.020" more lift and > 5* duration so they are not the same.

Claims that a manufacturer would leave 75+ ft-lbs of torque on the table by installing a terrible intake filter or muffler are grossly exaggerated.

[Fast355]

The numbers I posted are for the truck L31, not the marine engine. The marine cam had > 0.020" more lift and > 5* duration so they are not the same.

Claims that a manufacturer would leave 75+ ft-lbs of torque on the table by installing a terrible intake filter or muffler are grossly exaggerated.

The last line you just said is laughable....There are plenty of engines that can gain that kind of power with OEM vs Aftermarket intake and exhaust. My Infiniti M56 is the perfect example of that. It had 2 small panel filters, intake hoses that were smaller than the throttle body opening and had accordions, and then the exhaust had a horrible 1 7/8" to 2.5" Y-pipe, 2 resonators with a 1.5" ID core, and restrictive mufflers. I gained 8 rwhp form K&N filters. Replacing the stock intake ducts with HPS silicone intake tubes gained another 12 RWHP. 30 rwhp from a 2.5" dual exhaust with X-pipe and magnaflow setup after the manifold cats. I gained 50 hp at the tires without touching the long block or the tune. At a 20% drivetrain loss that is 62.5 hp at the crankshaft on a engine that was making about 450 hp out of the box despite its 420 hp rating. Magazine testing shows the 4,200 lbs car ran about a 13.4 @ 106 STOCK. I have run a 12.4 @ 110 mph in the car.

As for your cam spec difference. Having run both cams in the same setup, the cam does not make 10-15 HP or TQ difference one way or the other. The only reason I even swapped in the Marine cam at the time is I had destroyed 2 different aftermarket cams in the engine. The Marine cam was $150 for a GM billet steel roller cam. The marine vs automotive difference is mostly the intake manifold and exhaust difference between them.

[Fast355]

For what it is worth this article almost EXACTLY matches a setup I ran on one of the L31s. Set it up for a friend of mines class c motorhome based off a 2002 Express van. Basically a .030" over STOCK rebuild with 1.56" compression height pistons, .016" steel shim head gaskets, and the marine cam. It did 230 RWHP @ 4,400 rpm and 304 RWTQ @ 3,400 rpm on 87 octane after some tuning. Using the stock L31 truck intake manifold, tri-y headers, stock cats, stock muffler, and a tuned 0411. His van probably loses more like 30% through the driveline as well. 4L80E and GM 4.56 10.5" 14-bolt full floater. I also know the HD clutch fan eats some HP off the crank.

http://www.hotrod.com/articles/how-t...l-block-chevy/

[lionelhutz]

I DON'T CARE ABOUT YOUR CLAIMS. It would be easy to match any of those claims with a modified LQ4, especially when using a very generous dyno.

[Fast355]

I DON'T CARE ABOUT YOUR CLAIMS. It would be easy to match any of those claims with a modified LQ4, especially when using a very generous dyno.

The stock cam LQ4 will NOT match a stock cam 5.7 Vortec under 3,500 rpm, the LQ9 does not even do it. As you start increasing the cam, you lose torque on the 6.0L. Same dyno, same day the L31 made more torque at 3,400 rpm than the LQ9 did until it hit 4,000+ rpm. Peak torque on both was very similar. 304 vs 310 ft/lbs. Same dyno, same day. The LQ9 truck had the advantage of having a 4L60E and 8.5" 10-bolt to the 4L80E and 9.5" of the L31 as well. The L31 truck also had a mechanical fan where the LQ9 truck had OEM electrics. BOTH trucks had long tubes, decent exhaust, and were tuned. The 350 truck made about 230 HP and the 6.0L right at 260. Both had factory air intakes and air cleaners. For comparison my 2006 Hemi Ram with the stock cam and long tubes was run on the same dyno a few years before in the same summer weather. 285 rwhp and 301 rwtq. The Hemi is no different than the LS as far as powerband as it did not reach peak torque until 4,500 rpm. I saw a big cammed 5.3 truck run on the same day as the 5.7 and 6.0 and it put down 288 rwhp, but did not make more than 270 rwtq. The dyno I run on is far from generous. My friends 1997 C1500 with 6.0 LQ4 running a 230/235 @ .050 cam did not crack 300 RWHP on it! My M56 cracked 300 RWHP before it even hit 4,500 rpm.

You act like I hate the 6.0L so much. I am actually swapping one into something for my brother to have as a cross country travel vehicle. Its getting a TBSS intake, 8.1 injectors, Custom MAP SD operating system with the MAF deleted due to the way I am setting up the air intake, 2002-2004 LS6 cam, 0.020" milled 317s with some port smoothing/blending, and 1 3/4" shorty headers into 2.5" pipes and a dual 2.5" in/single 3" out muffler. Stock 4L80E is going behind it with a B82 converter and keeping the 3.08 gears in the 8.5. Honestly if I had another 5.7 Vortec hanging around and had not picked up this LQ4 for chump change, I would be swapping a 5.7 Vortec into this and keeping the TBI fuel system. I am not expecting the thing to wake up until the 3,500+ RPM range but once it gets there it should have no problem pulling into the 6,000-6,200 rpm range.

Also just speaking honestly here, the thing would have a VK56VD in it if they were not so hard to package or run in a non-OEM vehicle. You can get the 420 HP rated VK56VD close to the 500 hp / 500 tq mark without lifting a valve cover off it. When the VK56DE rated 317 HP was tested by CORE engine developments for building the CORE race trucks, it made nearly 450 HP in testing with an IR intake manifold & throttle bodies, long tubes, and an aftermarket ECU controlling it.

Their is nothing special about the 6.0L in my eyes. My own 1983 G20 van I am building has a 8.1 sitting in it with a GM 450 HP 502 HO cam in it. Something about 550 ft/lbs of torque @ 3,500 rpm just seems appealing to me.